Ed Huntress fired this volley in news: snipped-for-privacy@4ax.com:
That's why a good pump with a fresh oil change will do 20 microns. Mine will, and I only paid $169 for it. I'm not happy with a system until it will hold 50 microns after I turn off the pump.
Lloyd
What do you use to measure 50 microns? My best 6" diameter mechanical absolute pressure gauge stops at 100, and I don't have mercury for a McLeod gauge.
"Jim Wilkins" fired this volley in news:jrq7nj$15n $ snipped-for-privacy@dont-email.me:
A thermistor micron gauge.
It heats a thermistor with a regulated voltage through a fairly high- value precision (and temperature compensated) resistor, introducing a variable (very small) current depending upon the thermistor's temperature. Gas molecules rob heat from it, changing the resistance, and thus changing the current, which is measured to determine the state of the thermistor.
They can go down to 2 microns with very good accuracy. Mine is a Robinaire, and cost about $90 from a discounter.
Lloyd
"Stormin Mormon" wrote in news:7GZDr.7949 $ snipped-for-privacy@news.usenetserver.com:
Now you're changing the conditions.
Originally, you suggested that a gauge reading in inches couldn't be used to measure vacuum, which it obviously can.
More explicitly;
600 microns = 0.6mm, or 0.6 * .03937 = 0.0236" of Hg, or 13.6 * 0.0236" = 0.32" of water, to the nearest scale division.The full scale on that gauge is 1" of water.
jsw
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